Thread: using newton raphson method

thanks.. yeah.. i am trying it. but i cant create the polynomial of nthe degree where user will input the value of 'n'.. i am almost a beginner..
it will be good if u help me with this.plzz

this is not running properly..
please correct the codes...and help me in creating the interval...please


#include<stdio.h>
#include<conio.h>
#include<math.h>
#define MAX 50
#define eps 1e-6
void ReadPolynomial(int);
void BisectionMethod(int,double,double);
int arr[MAX];
double a,b;
void main()
{
int deg;
clrscr();
printf("\nEnter degree of equation : ");
scanf("%d",&deg);
ReadPolynomial(deg);
BisectionMethod(deg,a,b);
getch();
}
void ReadPolynomial(int deg)
{
int i,j,terms;
terms = deg+1;
for(i=0;i<terms;i++)
{
printf("\nEnter coefficient of x raised to the power %d : ",i);
scanf("%d",&arr[i]);
}
}

void BisectionMethod(int deg,double a,double b)
{
double x1,dx,fa,fx1,f;
int nstep,i,j,terms;
terms=deg+1;
dx=b-a;
nstep=0;
f=1.0;
fa=fx1=0.0;
printf("\n\n\nBISECTION METHOD : \nn\ta\t\tb\t\tx1\n");
while(fabs(dx)>eps)
{
x1=(a+b)/2;
for(i=0;i<terms;i++)
{
for(j=0;j<i;j++)
f=f*a;
f=f*arr[i];
fa+=f;
}
for(i=0;i<terms;i++)
{
for(j=0;j<i;j++)
f=f*x1;
f=f*arr[i];
fx1+=f;
}
if((fa*fx1)<0)
{
b=x1;
dx=b-a;
}
else
{
a=x1;
dx=b-a;
}
nstep++;
printf("\n%d\t%lf\t%lf\t%lf",nstep,a,b,x1);
}
printf("\nFinal Root : %lf", x1);
}

Please use the [code][/code] tags around your source, it makes it easier for everyone to read.

Code:

#include<stdio.h>
#include<conio.h>
#include<math.h>
#define MAX 50
#define eps 1e-6
void ReadPolynomial(int);
void BisectionMethod(int,double,double);
int arr[MAX];
double a,b;
void main()
{
  int deg;
  clrscr();
  printf("\nEnter degree of equation : ");
  scanf("%d",&deg);
  ReadPolynomial(deg);
  BisectionMethod(deg,a,b);
  getch();
}
void ReadPolynomial(int deg)
{
 int i,j,terms;
 terms = deg+1;
 for(i=0;i<terms;i++)
 {
  printf("\nEnter coefficient of x raised to the power %d : ",i);
  scanf("%d",&arr[i]);
 }
}

void BisectionMethod(int deg,double a,double b)
{
  double x1,dx,fa,fx1,f;
  int nstep,i,j,terms;
  terms=deg+1;
  dx=b-a;
  nstep=0;
  f=1.0;
  fa=fx1=0.0;
  printf("\n\n\nBISECTION METHOD : \nn\ta\t\tb\t\tx1\n");
  while(fabs(dx)>eps)
	{
	 x1=(a+b)/2;
	 for(i=0;i<terms;i++)
	 {
	  for(j=0;j<i;j++)
		f=f*a;
	  f=f*arr[i];
	  fa+=f;
	 }
	 for(i=0;i<terms;i++)
	 {
	  for(j=0;j<i;j++)
		f=f*x1;
	  f=f*arr[i];
	  fx1+=f;
	 }
	  if((fa*fx1)<0)
	  {
		b=x1;
		dx=b-a;
	  }
	 else
     {
      a=x1;
      dx=b-a;
     }
	 nstep++;
	printf("\n%d\t%lf\t%lf\t%lf",nstep,a,b,x1);
  }
 printf("\nFinal Root : %lf", x1);
}

ok... can u please help!!!??

At a quick glance, I can't see what's wrong with it.
Why isn't it working? What incorrect outputs are you getting? What should the correct outputs be?

Originally Posted by Jamdog

Please use the [code][/code] tags around your source, it makes it easier for everyone to read.

Code:

#include<stdio.h>
#include<conio.h>
#include<math.h>
#define MAX 50
#define eps 1e-6
void ReadPolynomial(int);
void BisectionMethod(int,double,double);
int arr[MAX];
double a,b;
void main()
{
  int deg;
  clrscr();
  printf("\nEnter degree of equation : ");
  scanf("%d",&deg);
  ReadPolynomial(deg);
  BisectionMethod(deg,a,b);
  getch();
}
void ReadPolynomial(int deg)
{
 int i,j,terms;
 terms = deg+1;
 for(i=0;i<terms;i++)
 {
  printf("\nEnter coefficient of x raised to the power %d : ",i);
  scanf("%d",&arr[i]);
 }
}

void BisectionMethod(int deg,double a,double b)
{
  double x1,dx,fa,fx1,f;
  int nstep,i,j,terms;
  terms=deg+1;
  dx=b-a;
  nstep=0;
  f=1.0;
  fa=fx1=0.0;
  printf("\n\n\nBISECTION METHOD : \nn\ta\t\tb\t\tx1\n");
  while(fabs(dx)>eps)
	{
	 x1=(a+b)/2;
	 for(i=0;i<terms;i++)
	 {
	  for(j=0;j<i;j++)
		f=f*a;
	  f=f*arr[i];
	  fa+=f;
	 }
	 for(i=0;i<terms;i++)
	 {
	  for(j=0;j<i;j++)
		f=f*x1;
	  f=f*arr[i];
	  fx1+=f;
	 }
	  if((fa*fx1)<0)
	  {
		b=x1;
		dx=b-a;
	  }
	 else
     {
      a=x1;
      dx=b-a;
     }
	 nstep++;
	printf("\n%d\t%lf\t%lf\t%lf",nstep,a,b,x1);
  }
 printf("\nFinal Root : %lf", x1);
}

I hope you don't mind my using Jamdog's version since it's a pleasure to look at.

I've gone through the trouble to verify that double a and double b are both zero
in your function BisectionMethod. Checking back, although a & b are both global variables,
where are they initialized?

Also frustrating me, my compiler should have squawked about this... warnings are on
high.... reason why I had to manually search for this.

okk... but can you please correct the mistakes..!!??

Originally Posted by sanskaar

okk... but can you please correct the mistakes..!!??

I SPENT over an HOUR finding your mistake.

NOW you want me to correct it?

noo.... just tell me what should i do??
i have made changes in a and b but still cannot find the correct answer...!!
please....!!

yes, i got the answer now.... and found my mistakes..
sorry...!!
n thanx Char*Pntr... .
but still one problem...i have to calculate the interval in which the roots lie of the equation lie by passing a function..
can you all please give some idea of how to do that in this same program code...??

i made the changes... and this program is working fine.
but i am providing the intervals myself in the function bisection method. i dont have to do that i have to pass a function within the main function to calculate the interval,and frankly speaking i have no idea how to do that. please give me some ideas....
here is the changed program code..

Code:

#include<stdio.h>
#include<conio.h>
#include<math.h>
#define MAX 50
#define eps 1e-6
void ReadPolynomial(int);
void BisectionMethod(int,double,double);
int arr[MAX];
void main()
{
  int deg;
  double a,b;
  clrscr();
  printf("\nEnter degree of equation : ");
  scanf("%d",&deg);
  ReadPolynomial(deg);
  BisectionMethod(deg,a,b);
  getch();
}
void ReadPolynomial(int deg)
{
 int i,j,terms;
 terms = deg+1;
 for(i=0;i<terms;i++)
 {
  printf("\nEnter coefficient of x raised to the power %d : ",i);
  scanf("%d",&arr[i]);
 }
}

void BisectionMethod(int deg,double a,double b)
{
  double x1,dx,fa,fx1,f;
  int nstep,i,j,terms;
  a=0.0, b=1.0;
  terms=deg+1;
  dx=b-a;
  nstep=0;
  f=1.0;
  fa=fx1=0.0;
  printf("\n\n\nBISECTION METHOD : \nn\ta\t\tb\t\tx1\n");
  while(fabs(dx)>eps)
	{
	 x1=(a+b)/2;
	 for(i=0;i<terms;i++)
	 {
	  for(j=0;j<i;j++)
		f=f*a;
	  f=f*arr[i];
	  fa+=f;
	 }
	 for(i=0;i<terms;i++)
	 {
	  for(j=0;j<i;j++)
		f=f*x1;
	  f=f*arr[i];
	  fx1+=f;
	 }
	  if((fa*fx1)<0)
	  {
		b=x1;
		dx=b-a;
	  }
	 else
	  {
		a=x1;
		dx=b-a;
	  }
	 nstep++;
	printf("\n%d\t%lf\t%lf\t%lf",nstep,a,b,x1);
  }
 printf("\nFinal Root : %lf", x1);
}